Manufacture of halopropane



2 Claims. (Cl. 260--653) This invention relates to the hydrogenation of1,2,2

trichloropentafluoropropane, OF CCl CClF and is more particularlydirected to 1,2,2 trihydropentafluoropropane CF CH CHF a new product,and to processes for making this compound and 2 monohydropentafluoropropene, OF CH=CF Objects of the invention include provision of 1,2,2trihydropentafluoropropane as a new compound, and pro- -vision of easilycontrollable, catalytic gas-phase methods for making CF OH CHF and OFCH=CF In accordance with the invention, it has been found that, by useof certain catalysts and gas-phase reaction conditions, hydrogen may bedirectly substituted for the chlorine of 1,2,2trichloropentafluoropropane, and that 1,2,2 tn'hydropentafluoropropane,2 monohydropentafiuoropropene, and 2 monochloropentafluoropropene ifdesired, may be made by direct catalytic gas-phase hydrogenation of1,2,2 tiichloropentafluoropropane.

The invention comprises the discovery of the adapta- ;bility of CF CClCClF as an organic starting material, and the discovery of particularcatalysts and catalytic "reaction conditions, which factors of startingmaterial,

catalysts and reaction conditions conjunctively afr'ord accomplishmentof the invention objectives.

Practice of the invention comprises hydrogenating j1,2,2trichloropentafiuoropropane by subjecting the same under certaintemperature conditions and while in the presence of certain catalysts tothe action of hydrogen in quantity and for a time sufiicient to effectformation of a substantial amount of a hydrogenated straight-chain threecarbon atom hydrocarbon consisting of carbon, fluorine, and hydrogen andhaving respective terminal carbon atoms triand difluorinated and thesaid difluorinated carbon atom containing from zero to one hydrogenatom, and recovering such hydrogenated hydrocarbon, which may be CF CHCHF or CF CH=CF or mixtures thereof, from the resulting reactionproducts.

The organic starting material, 1,2,2 trichloropentafiuoropr opane, CFCCl CClF a known compound, is .a

colorless liquid boiling at 72 C. Reactions elfected during practice ofthe invention may be represented by An important feature of theinvention is the nature of the catalytic material employed and thecomposition thereof. This catalyst consists of palladium supported onactivated carbon. It has been found that the cata .lysts describedafford two marked advantages, namely,

facilitate use of moderate reaction temperatures, and effeet high yieldsof sought-for products, which yields, within limits may be madeselective by alteration of reac- U tion conditions. With regard topreparation of the catalys t, a water-soluble palladium salt which iscapable of jr eduction to elemental palladium by hydrogen may be2,942,036 Patented June 21, 1960 employed. Readily available palladiumchloride is preferred. Any of the commercial activated carbons may beused, e.g. Columbia 6G Carbon, Columbia SW Carbon, or Darco Carbon. Ifdesirable, the activated carbon may be treated preliminarily to removeany silica by leaching with aqueous HF, water washing, and drying. Thegranular, activated carbon support may be immersed in an aqueoussolution of palladium chloride. The carbon, carrying absorbed palladiumchloride, is separated from the water and preliminarily dried at aboutC. The catalyst may then be heated at temperatures of say -300 C. in astream of hydrogen to eliminate water and reduce the palladium salt toelemental palladium. The amounts of palladium employed may be such thatthe finished palladium on activated carbon catalyst containssubstantially in the range of 110.0 weight percent of metallicpalladium, balance carbon. Within these limits, palladium content doesnot appear to be particularly critical, although we find that to obtainoptimum resuts, the preferred range of palladium concentration liessubstantially in the range of about 2-5 weight percent of palladium.

Practice of the invention procedurally comprises pass= ing a gas-phasemixture of CF CCl CClF and hydrogen thru a reaction zone containing thecatalyst indicated 'and maintained at moderately elevated temperatures,and recovering CF CH CHF or CF CH=OF or both from the reaction zoneexit. Any CF CCl=CF formed may be recovered and utilized as such, e.g.as a grain fumigant, or may be recycled along with unreacted CF CC1 CClFApparatus may comprise preferably a tubular reactor, made of nickel orother suitable material such as Inconel, Monel and stainless steel,mounted in a furnace provided with means for maintaining the reactionzone in the reactor at the desired elevated internal temperature. Thereactor may include inlets for introduction of controlled amounts ofhydrogen and vaporous CF CC1 CClF and may be provided with a reactionproduct exit connected to a more or less conventional product recoverysystem.

Significant reaction and substitution of hydrogen for chlorine areelfected at temperatures as low as about 150 C., although forcommercially substantial results, temperatures are preferably not lessthan about C. In general, increase in temperature increases hydrogensubstitution, and temperatures as high as about 400 C. may be employedwithout effecting too undesirable decomposition. However, withreasonably suitable hydrogen concentration and residence time noparticular advantages accrue by use of temperatures: in excess of about350 C. Accordingly, preferred temperatures lie substantially in therange of 175350 C.

Hydrogen may be employed in any quantity sufiicient to react with asignificant amount of the CF CCl CC-lF starting material. Stoichiometricamounts; of reactants are noted above. Hydrogen to organic startingmaterial mol ratios may be varied considerably and lie within the rangeof about 1.5 to 4 mols of hydrogen per mol of organic starting material.To avoid high reaction temperature and to minimize or substantiallyeliminate formation of CF CCI=CF if this product is not desired, it ispreferred to emploly hydrogen in such quantity as to provide in thereaction zone about 2.5 to 4 mols of hydrogen per mol of organicstarting material.

Contact or residence time necessary to efifect a desired percentage ofreaction is dependent to some extent upon temperature and hydrogenconcentration. Thus, increased temperature and hydrogen concentrationfacilitate shorter contact time and vice versa. In view of theinterdependent relation of temperature, hydrogen to organic startingmaterial mol ratio, and residence time,

" 0.037 fmol of CF CH=CF and CF CH CHF "recovered quantitiesrepresentedabout 1516% of the demonstrated by dependent examples, it has been foundpossible to carry out the reaction under sufiiciently high hydrogenconcentration conditions substantially in the range of3-4 m'ols ofhydrogen per'mollof CF CC1 CClF and under sufficien tly-high temperatureconditions substantially in the range of 25035() C., and for a residencetime sufficiently long to efiect formation of reaction zone exit"products containing a dominant weight proportion of'CF cHgCl-lF Thus,by sufficient increase of temperature and/or hydrogen concentration, thereaction'may be carried out so as to effect formation of reaction zoneexitwproducts containing a dominant weight proportion of CFgCH CHF and,if desired, no significant amount of CF CCl=CF Contact time may lie inthe range of 2'to 20 seconds, preferably 5 to second's. Depending uponthe composition and relative quantities of. products desired, withregard to temperature, mol ratio of hydrogen to organic startingmaterial, contact time, and catalyst composition with respect topalladium, optimum conditions may be determined by test run.

. Materials exiting the reaction zone comprise soughtfor productsif'desired, 'HCl, and any unreacted starting material and hydrogen. Exitproducts of the reactor may be passed into a water scrubber whichremoves most of the HCl, thru-a-20% NaOH solution which removes lasttraces of acid, thru'a CaCl drying tower, and thence into a cold trap'cooledb'y a Dry Ice-acetone mixture. Any unreacted hydrogen passes thruthe cold trap unabsorbed. The various constituents of the cold trapcondensate may be recovered and isolated by fractional distillation.*Any'unreacted starting material which might collect in the waterscrubber may be recovered by conventional methods.

The following illustrate practice of the invention. Pericen'tages are byweight unless otherwise indicated.

Example 1.A catalyst consisting of 3% by weight metallic palladiumsupported on 8-10 mesh Columbia Carbon Grade 6G was preparedsubstantially as above described. About 90 cc. of such catalyst weredisposed in a'central 18 inch long length of a 0.5 inch I.P.S. nickelpipe reactor 36 inches long heated externally over 24 inches of lengthby an electric furnace provided with automatic temperature control. Thereactor was provided 'atone end'with suitable inlets for hydrogen andorganic starting material, and the other end with a pipe connection to aproducts recovery unit. During about 6.5

hours a 'vaporous mixture of about 347 g. (1.46 mols) of CF CCl CC1F and4.9 mols of hydrogen were passed "at about constant rate into thereactor. of hydrogen to organic material was about 3.311, and

Molecular ratio residence time in the reactor was about 8 seconds.Throughout the run temperature was maintained substantially in-the rangeof 175190 C. Exit products of the reactor were passed thru a waterscrubber which removed mostof the HCl, through a 20% NaOH solution whichremoved last traces of acid, thru a CaCl drying *tower,and thence into-acold trap cooled by a Dry Iceacetone mixture, the gaseous exit of thecold trap being unutilized'hydrogen. About 190 g. of condensate,recovered in the-cold trap, were subjected to fractional distillation.There were recovered about 29 g. (0.216 mol) of CF CH=CF boiling atabout minus 22 C.; about 22g; (0.183 mol) of material boiling in therange of about minus 22 C. to plus 13 C.; about 108 g.

(0.805 mol) ofmaterial boiling at about 14 C. and identified as CF CHCHF and about 22 g. (0.093 mol) er unreacted cr ccnccin startingmaterial. Sample loss was about 9 g. The minus 22-plus 13 C. fractioncomprised about 0.146 mol of CF CCl CF plus about These .tedorganic.startingmaterialconverted to ,pentafluoropropene, CF CH==CF about 60%to 1,2,2 trihydropentafluoropropane, CF CH CHF approximately 10% tomonochloroperfluoropropene, and about 6-7% of unreacted startingmaterial. Overall conversion of starting material to reaction productswas about 86%, and overall recovery of organic material was-about 93%.Hydrogen utilization was about61 62%. Molecular weight deter minationwith regard to the 14 C. CF CH CHF fraction indicated a value of about134. "Infraredanalysis showed presence ofhy'dro'gen and C--F bonds withno uns-aturation.

Example 2-.--Apparatus, catalyst, reaction temperature and residencetime were the same as inExample 1. During about 4.5 hours a vapor'ousmixture of about 374 g. (1.54 mols) of CF CCl CClF and 3.3 mols ofhydrogen were passed at about constant rate into the reactor. Molecularratio 'of hydrogen to organicmaterial was about -2.1:-l. Exitproducts ofthe reactor were handled as :in Example 1. About 229 g. of condensate,recoveredrin the cold trap, were subjected to fractional distillation.There were recovered about 54 g. (0.410 mol.) of CF CH=CF boiling atabout minus 22 C.; about-9.1g.

(0.565 mol) ofmaterial boiling inthe range of about minus 22 C. to plus13 C.; about 31g. (0.232 mo1):.of material boiling at about 14 C. andidentified "as CF CH CHF and about 43 g. (0.185 mol) of unreacted CF CClCClF starting material. Sample lossineluding about a 6 g. forerun, wasabout 10 g. The'minus 22-plus 13 C. fraction comprised about 0.452 molof CF CCl=CF and about 0.113 mol of CFggCHzCHFg. These'recoveredquantities represented about 26-27% of the fed organic starting materialconverted .to .penta fluoropropene, 22-23% to 1,2,2trihydropentafluoroproof hydrogen to organic material was about 3.7:.1.

Throughout the .run temperature was maintained .at about325 C. Exitproducts of the reactor Werehandled as in Example .1. .About 159 g. ofcondensate, recovered in the cold trap, were subjected to fractionaldistillation. There were recovered about 49 g. of a CF CH=CE fractionboiling at about minus 22 C.; about 29 g. ofa

.fraction boiling in the range of about minus 22 C. to

plus 13l4 C.; about 82 g. (includinga 13g. hold-up) of material boilingat about l414.5 C. and identified as'CF CH CHF and no unreacted CF CCICCIF starting material. The 29 g. fraction, boiling at about-minus 22 ato plus 13-14" C. contained no recoverable CF CCl=CF and comprised aboutequal weight parts of CF CH=CF and CF CH CHF These quantities representabout0485 mol recovery of-CF CH=CF and 0.715 mol recovery of CF CH CHFPercentagewise, the quantities represent about 4041% of the fed organicstarting material converted to pentafluoropropene, and

about 59-60% to 1,2,2 trihydropentafluoropropane. Overall conversionofstarting material to reaction prodnets and overall recovery of organicmaterial were practically Hydrogen utilization was about 71%.

CF CH CHF being a colorless non-flammable liquid having a boiling pointof 14 C., is notably adaptable for use as a diluent of propellents suchas CCI F CHCI F,

and CHgCClF used in aerosol formulationsgfunctioning similarly to theWell known CCl F. CF CH CHF- 'is especially suitable for this purposebecause the presence of "hydrogen in the molecule increases miscibilitywi'th and solubility of many diluting and active constituents, such ashydrocarbons, plasticizers, polymers, and insecticides, commonly used inaerosol compositions. CF CH=CF is useful in the production of copolymersof CF CH=CF and CCIF CF which copolyrners may be made by conventionalpolymerization processes employing redox catalyst, and Which copolyrnersare useful in the preparation of molded products and coatingapplications for corrosion protection, e.g. Wire coating.

We claim:

1. The process of hydrogenating 1,2,2 trichloropentafluoropropane whichcomprises subjecting the same, at temperatures substantially in therange of 175359 C. and while in the presence of palladium-activatedcarbon catalyst, to the action of hydrogen in quantity and for a timesufiicient to effect formation of a substantial amount of a hydrogenatedstraight-chain three carbon atom hydrocarbon consisting of carbon,fluorine and hydrogen and having respective terminal carbon atoms trianddifiuorinated and the said difiuorinated carbon atom containing fromzero to one hydrogen atoll, and recovering such hydrogenated hydrocarbonfrom the resulting reaction products.

2. The process of hydrogenating 1,2,2 trichloropentafluoropropane whichcomprises subjecting the same, While in the presence ofpalladium-activated carbon catalyst,

to the action of hydrogen, under sufficiently high hydrogenconcentration conditions substantially in the range of 3-4 rnols ofhydrogen per rnol of CF CC1 CClF and under sufl'iciently hightemperature conditions substantially in the range of 250-350" C. and forresidence time sufiiciently long, to effect formation of reactionproducts containing a dominant Weight proportion of CF CH CHF andrecovering CF CH CHF from such reaction products.

References Cited in the file of this patent UNITED STATES PATENTS2622-6, only p. 2624 needed.

Haszeldine et 211.: Four. Chem. Soc. (London), 1954, pp. 923-5, only p.923 needed.

Simons: Fluorine Chemistry, Academic Press N.Y., vol. I, p. 501.

Inc,

1. THE PROCESS OF HYDROGENATING 1,2,2 TRICHLOROPENTAFLUOROPROPANE WHICHCOMPRISES SUBJECTING THE SAME, AT TEMPERATURES SUBSTANTIALLY IN THERANGE OF 175-350*C. AND WHILE IN THE PRESENCE OF PALLADIUM-ACTIVATEDCARBON CATALYST, TO THE ACTION OF HYDROGEN IN QUANTITY AND FOR A TIMESUFFICIENT TO EFFECT FORMATION OF A SUBSTANTIAL AMOUNT OF A HYDROGENATEDSTRAIGHT-CHAIN THREE CARBON ATOM HYDROCARBON CONSISTING OF CARBON,FLUORINE AND HYDROGEN AND HAVING RESPECTIVE TERMINAL CARBON ATOMS TRIANDDIFLUORINATED AND THE SAID DIFLUORINATED CARBON ATOM CONTAINING FROMZERO TO ONE HYDROGEN ATOM, AND RECOVERING SUCH HYDROGENATED HYDROCARBONFROM THE RESULTING REACTION PRODUCTS.